Rapid and accurate diagnostic technologies for early-state identification of cardiovascular abnormalities have become of high importance to prevent and attenuate their progression. The capability of biosensors to determine an increase in the concentration of cardiovascular protein biomarkers in circulating blood immediately after a myocardial infarction makes them ideal point-of-care platforms and alternative approaches to electrocardiograms, chest X-rays, and different laboratory-based immunoassays. We report here a generic approach toward multianalyte sensing platforms for cardiac biomarkers by developing aptamer-based electrochemical sensors for brain natriuretic peptide (BNP-32) and cardiac troponin I (cTnI). For this, commercial gold-based screen-printed electrodes were modified electrophoretically with polyethyleneimine/reduced graphene oxide films. Covalent grafting of propargylacetic acid integrates propargyl groups onto the electrode to which azide-terminated aptamers can be immobilized using Cu(I)-based “click” chemistry. To ensure low biofouling and high specificity, cardiac sensors were modified with pyrene anchors carrying poly(ethylene glycol) units. In the case of BNP-32, the sensor developed has a linear response from 1 pg mL–1 to 1 μg mL–1 in serum; for cTnI, linearity is observed from 1 pg mL–1 to 10 ng mL–1 as demanded for early-stage diagnosis of heart failure. These electrochemical aptasensors represent a step further toward multianalyte sensing of cardiac biomarkers.

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We report the use of Co-porphyrins as electrochemical tags for a highly sensitive and selective genosensor. An avian influenza virus-based DNA sequence characteristic of H5N1 was detected at femtomolar levels from competing non-complementary sequences through hybridisation with the labeled DNA.

The working principle of a genosensor is based on the mechanism of ion‐channel mimetic sensors. The analytical signals generated upon hybridization processes were recorded by a redox active marker [Fe(CN)6]3−/4− present in the sample solution using voltammetric techniques. The developed genosensor was suitable for determination of 20‐mer complementary oligonucleotide sequence, and also of the PCR products containing the complementary 20‐mer sequence in various positions, with detection limits in the 10 pM range. The noncomplementary 20‐mer oligonucleotide sequence as well as the PCR product without complementary region generated very weak response. The good discrimination of the position of the complementary part in the PCR products was observed.

The duo-genosensor consisting of two different oligonucleotide probes immobilized covalently on the surface of one gold electrode via Au-S bond formation was used for simultaneous determination of two different oligonucleotide targets. One of the probes, decorated on its 5'-end with ferrocene (SH-ssDNA-Fc), is complementary to the cDNA representing a sequence encoding part of H5 hemagglutinin from H5N1 virus. The second probe, decorated on its 5'-end with methylene blue (SH-ssDNA-MB), is complementary to cDNA representing the fragment of N1 neuraminidase from the same virus. The presence of both probes on the surface of gold electrodes was confirmed with Osteryoung square-wave voltammetry (OSWV). The changes in redox activity of both redox active complexes before and after the hybridization process were used as analytical signal. The peak at +400 ± 2 mV was observed in the presence of 40 nM ssDNA used as a target for SH-ssDNA-Fc probe. This peak increased with the increase of concentration of target ssDNA. It indicates the "signal on" mode of analytical signal generation. The peak at -250 ± 4 mV, characteristic for SH-ssDNA-MB probe, was decreasing with the increase of the concentration of the complementary ssDNA target starting from 8 to 100 nM. This indicates the generation of electrochemical signal according to the "signal off" mode. The proposed duo-genosensor is capable of simultaneous, specific, and good sensitivity probing for the sequences derived from genes encoding two main markers of the influenza virus, hemagglutinin and neuraminidase.

In this work, we report on oligonucleotide probes bearing metallacarborane Furthermore, the proposed genosensor was suitable for discrimination of PCR products with different location of the complementarity region.2

Electrochemical biosensors have emerged as reliable analytical devices suitable for pathogen detection. Low cost, small sample requirement and possibility of miniaturization justifies their increasing development. Thus, we report in this review on the state of the art of avian influenza virus detection with genosensors and immunosensors working by an electrochemical mode. Their working principles focusing on the physical properties of the transducer, the immobilization chemistry, as well as new trends including incorporation of nanoparticles will be presented. Then, we critically review the detection of avian influenza virus in the complex matrices that use electrochemical biosensors and compare them with traditionally applied methods such as ELISA or Western blot.

Suitable immobilization of a biorecognition element, such as an antigen or antibody, on a transducer surface is essential for development of sensitive and analytically reliable immunosensors. In this review, we report on (1) methods of antibody prefunctionalization using electroactive probes, (2) methods for immobilization of such conjugates on the surfaces of electrodes in electrochemical immunosensor construction and (3) the use of antibody-electroactive probe conjugates as bioreceptors and sensor signal generators. We focus on different strategies of antibody functionalization using the redox active probes ferrocene (Fc), anthraquinone (AQ), thionine (Thi), cobalt(III) bipyridine (Co(bpy)33+), Ru(bpy)32+ and horseradish peroxidase (HRP). In addition, new possibilities for antibody functionalization based on bioconjugation techniques are presented. We discuss strategies of specific, quantitative antigen detection based on (i) a sandwich format and (ii) a direct signal generation scheme. Further, the integration of different nanomaterials in the construction of these immunosensors is presented. Lastly, we report the use of a redox probe strategy in multiplexed analyte detection.